Snow detector and heater system for microwave antennas



May 18, 1954 E, DYKE T 2,679,004

SNOW DETECTOR AND HEATER SYSTEM FOR MICROWAVE ANTENNAS Filed Dec. 21, 1951 4 Sheets-Sheet l INVENTORS.

y 1954 E. DYIKE ET AL 2,679,004

SNOW DETECTOR AND HEATER SYSTEM FOR MICROWAVE ANTENNAS Filed Dec. 21, 1951 4 Sheets-Sheet 2 lrw l1;

y 8, 1954 E. DYKE HAL 2,679,004

SNOW DETECTOR AND HEATER SYSTEM FOR MICROWAVE ANTENNAS Filed Dec. 21, 1951 4 Sheets-Sheet 3 May 18, 1954 E. DYKE ETAL snow DETECTOR AND HEATER SYSTEM FOR MICROWAVE ANTENNAS Filed Dec. 21, 1951.

4 Sheets-Sheet 4 126 ewmm, g1

@chmffi )x W Patented May 18, 1954 SNOW DETECTOR AND HEATER SYSTEM FOR MICROWAVE ANTENNAS Edwin Dyke, Brookfield, and Richard Y. Hoffman, J r., Northbrook, Ill., assignors to Motorola, Inc., Chicago, 111., a corporation of Illinois Application December 21, 1951, Serial No. 262,876

12 Claims. 1

This invention relates generally to wave reflectors and more particularly to a heated reflector device for electrical microwaves for preventing the collection of ice and snow thereon. This application is a continuation in part of our co-pending patent application Serial No. 164,818, filed May 27, 1950.

Various reflecting structures have been provided for directing waves which are transmitted from one point to another. These structures have reflecting surfaces which are generally parabolic and operate to convert the waves from a small source to a parallel beam or conversely from a beam to a source. For electrical signalling and microwave frequencies such a reflector is used at the radiating and/or receiving antenna.

When such a reflector is used in the outdoors where it is exposed to rain, snow, sleet and the like, ice and snow will form on the reflecting surface and reduce the effectiveness thereof. This is particularly true when the reflectors are mounted horizontally as in such cases the reflector forms a container to hold the snow and water which freezes to form ice. Means for draining the reflector have been provided to remove water therefrom, but such means are not effective when the temperature is below freezing so that the water forms ice on the reflector surface. Also, falling snow or sleet will adhere to the surface and reduce the effectiveness thereof.

It is therefore an object of the present invention to provide an improved reflector system in which the accumulation of ice and snow on the reflected surface thereof is eliminated.

Another object of this invention is to provide an automatic heating system for a horizontally positioned outdoor antenna reflector which prevents the accumulation of ice and snow on the reflected surface thereof.

Still another object of this invention is to provide an automatic electric heating system for an antenna reflector having a control circuit for energizing the system so that it utilizes a minimum of power.

Another object of this invention is to provide an automatic control for an antenna reflector heating structure which will be responsive to the occurrence of precipitation in near freezing or below freezing temperatures to energize the reflector heater.

Yet another object of the invention is to provide a. device responsive to conditions caused by the occurrence of precipitation in near freezing or below freezing temperatures to provide a control for a remotely located system in accordance withthe occurrence of such conditions.

A feature of this invention is the provision of a reflector having a parabolic reflecting surface and an elongated heating element positioned adjacent to the back or convex surface thereof with the heating element being substantially uniformly positioned over the convex surface for heating the reflector, and an automatic control circuit for controlling one or more portions of the heating element.

Another feature of this invention is the provision of a heating system for a reflector in which a first heating element is controlled by the temperature about the reflector, and a second heating element is controlled in accordance with a condition at the reflecting surface. The second heating element may be controlled by the presence of ice or snow on the reflector surface, as indicated by a detector adjacent the reflector and having a surface exposed in the same manner as the reflector surface.

Yet another feature of the invention is the provision of a heated device which is adapted to melt snow or ice as it is precipitated, and to actuate electric control circuits in accordance with the presence of melted snow or ice.

Further objects and features and many advantages of the present invention will be apparent for a consideration of the following description when taken in connection with the accompanying drawings in which:

Fig. 1 illustrates the microwave station using a reflector in accordance with the invention;

Fig. 2 illustrates a heating system in which an auxiliary heater is energized when ice or snow forms on the reflecting surface;

Figs. 3 to 6 inclusive illustrate an embodiment of the system including a device for detecting ice or snow;

Fig. 7 is a perspective view of another construction of an auxiliary snow detector to be used with the reflector heater structure;

Fig. 8 is a longitudinal section of the snow detector of Fig. 7;

Fig. 9 is a section of the line 8@ of Fig. 8;

Fig. 10 is a section of the direction of the arrows on the line itili of Fig. 8; and

Fig. 11 is a wiring diagram of the snow detector of Fig. 7.

In practicing the invention there is provided an antenna reflector which is positioned horizontally to direct waves between an antenna and a flat reflector. The reflector has a concave parabolic reflecting surface which is directed upwardly and a convex back surface on which the heating element is positioned. The heating system may be wound in the form of a spiral and is positioned substantially uniformly over the area of the reflector. The heating element may be made up of a plurality of heating coils or portions which are separately controlled. In such cases, one of the coils may be energized when the outside temperature approaches freezing as for example at 35. The other coil may be operated by a separate control as for example by a. control responsive to the presence of ice and snow. The presence of ice and snow may be detected by heating a portion of the reflector or an adjacent surface to melt any ice or snow thereon. The water thus produced may be used to control the energization of a heating coil on the reflector.

A separate snow detector responsive to precipitation in near freezing or below freezing tern-- perature may be comprised of a heated funnel and a pair of carbon electrodes positioned beneath the funnel opening to receive therebetween the melted snow or ice and establish an electric circuit between the electrodes for controlling a relay system or the like.

Referring now to the drawings, in Fig. 1 there is illustrated a microwave system including trans-- mitting and /or receiving equipment It having 1 an antenna ll extending therefrom. A reflector I2 is provided for directing waves from the an tenna H toward a flat reflector I3. Received waves are also reflected by the flat reflectors itto the upwardly turned parabolic reflector i2 and thereby directed to the antenna ii. As shown in Fig. 1, the reflector includes a cup shaped member [5 having an upwardly curved concave surface which is of parabolic configuration. A housing [6 of frusto-conical shape has a rim H which is secured to the rim of the refleeting member l5. The housing it may be supported on the microwave equipment it by adjustable supports 18, or may be supported in any other suitable manner. An opening i9 is provided in the cup shaped member l5 and an opening 2i] is provided in the housing I 6 through which the antenna l I from the microwave equip" ment extends.

Openings 2| and 22 are provided in the cup shaped member and the housing l6, respectively, at the center thereof, through which water collecting in the reflector may be allowed to drain. A duct structure 23 is provided for carrying this water to the side so that it does not flow directly on the housing for the microwave equipment 10. To prevent ice and snow from collecting on the reflector member IS, an elon gated heating element 25 is wound in the form of a spiral on the underside of the reflector member.

In Fig. 2 there is disclosed a reflector heating system in which the heating element is formed by coils B5 and 61. The heating coil is connected to a source of power through thermostatic switch 66 and is positioned near the center of the reflector member about the center opening therein. A second heating coil 61 is provided extending from the first coil 65 to the edge of the reflector member. This second coil is connected to the source of power through the thermostatic switch 66 and also through a cell which is in series with the switch and the coil iii. The cell includes a container 69 having a pair of electrodes 70 positioned therein. The container 69 is placed below the opening 2! in the reflector member I5 so that any ice or snow on the reflector will be melted by heat from the coil 65, and the water resulting therefrom will flow into the c0ntainer'69 and provide a closed circuit be-- 4 tween the electrodes 10. This will cause energization of the coil 61 to heat the remainder of the reflector member. It is therefore seen that when ice or snow is present on the reflector, and the coil 55 is energized, the ice or snow will be melted causing the circuit through the coil 61 to be energized and the entire reflector member to be thereby heated. Since the coil 61 is also connected through the thermostatic switch 66, the coil 6'! will not be energized by the presence of water alone as might be produced by rain, when the temperature about the reflector is above that at which the thermostatic switch 66 will be closed. The second coil 61 may be controlled by a form of separate snow detector switch and circuit such as to be described in connection with Figs. 3 through 6 or '1 through ll of the drawings.

It may be preferable to provide the snow detector as a separate element instead or incorporating it with the antenna reflector itself. One form of such an arrangement is shown in Figs. 3 to 6 inclusive. In Fig. 3 the reflector member i5 is provided with a supporting housing 16. A single heating coil 15 is provided on the rear surface of the reflector for heating the same. The coil 15 is energized through the contacts it of relay ll so that when the relay 11 is energized the contacts T6 will close and the heating coil "l5 will be energized.

The relay H is part of an external snow detector device which is best shown in Figs. 4 and 5. The device includes a cylindrical housing til having a flat base 8! and a conical or funnel shaped top 82. Within the housing is a frame structure including the insulating members 83, 34 and 85. Supported on the insulating member 83 is a heating coil 86. As shown in Fig. 3, this heating unit 86 is connected through the thermostat 87 across an alternating current source so that when the temperature falls below a .predetermined value, the thermostat 81 will close and the heating unit 86 will be energized. The housing is lined with insulating material 19 to reduce the escape of heat through the cylindrical housing walls, and the heat therefore rises to heat the funnel-shaped member 82. This is effective to melt any ice or snow which may have formed on the funnel-shaped surface 82.

As shown best in Fig. 6, a V-shaped trough 8B is placed below the center of the member 82 so that any water appearing on the surface 82 resulting from the melting of ice or snow is carried down the trough 88 to the space between electrodes 89 and 90. The trough 88 serves as a windshield and serves to carry any drops from the funnel shaped surface 82 to the space between the electrodes 89 and 90. The bottom wall 3! includes openings therein to permit the escape of water therefrom.

As shown clearly in Fig. 3 the electrodes 89 and 9!] are connected in a series circuitacross the A. C. source which circuit includes rectifier ill, resistor 9?. and relay 93. The relay 93 is a very sensitive direct current relay which is actuated when a very small current is provided due to the drops of water bridging the electrodes 89 and 9G. It may be desired to provide a coating on the surface 32 which will be in part dissolved by the water thereon and will render the water more conductive when it flows between the electrodes. The rectifier 9| may be of the selenium type and is connected in a peak rectifying circuit including condenser 94. The manner in which these elements are supported and positioned in the housing is shown in Figs. '4 and 5.

The operation of the system of Figs. 3 to 6 inclusive is believed to be clear from the foregoing description and from a consideration of Fig. 3. The detector must be located adjacent the reflector with surface 82 positioned so that ice or snow will collect thereon under the same conditions as on the reflector. The heater unit 86 is energized by thermostat 3? when the temperature falls below a predetermined value. The thermostat may be set to energize the heater when the temperature falls below 35 F. as at higher temperatures than this snow and ice will not form on the antenna reflector. The thermostatic switch 81 also closes the circuit through the rectifier 9i, electrodes 89 and 90, and relay es, so that relay 93 will be actuated in the event that there is moisture on the surface 82 which flows between the electrodes 89 and 90 to close the circuit therethrough. The relay 93 includes contacts 96 which close to connect the heavy duty relay 11 across the alternating current source and this relay in turn connects the heating coil 1'5 on the surface of the antenna reflector to the alternating current power source.

In Figs. '7 through 11 a second form of snow detector is disclosed. A perspective view of the snow detector is shown in Fig. 7 with the outer cover removed in order to clearly show the assembled relation of the elements of the device. A funnel I65 which is preferably a casting of some highly heat conductive material such as aluminum is arranged to receive precipitation which may be in the form of snow or ice. A heater of the conventional metal sheathed type is embedded at It! in the funnel Elli) at the time that the funnel is cast. The heater llil is most clearly shown in Figs. 8 and 10 of the drawings and as shown in Fig. 11 of the drawings is adapted to be connected to a source of alternating current line voltage through a thermostatic switch Hi2 when the ambient temperature is or lower. As shown in Figs. '7 and 8 of the drawings the thermostatic switch I02 extends downwardly out of easing I03 to be directly exposed to the outside ambient temperature. As most clearly shown in Fig. 8 of the drawings, a disc baille [04 is seated on the cast ledge portions 85 to prevent any foreign solid materials other than melted ice or snow from passing through to the funnel opening lflfi.

Electrodes H31 and its preferably of carbon material are supported directly beneath the funnel opening Hi6 so that water from melted snow or ice will pass between the electrodes Hi1 and H18 in order to complete an electrical circuit between the electrodes. As shown most clearly in Figs. 8 and 9, electrode Nil is secured to the metal post lllii which is fastened at lit to the base of the funnel [08. An insulating space member HI is fastened to the electrode iii! and the electrode it?! is secured to the insulating spacer II! as shown in Fig. 9. In such an arrangement the electrode I0! is grounded to the metal structure of the snow detector while the electrode its is insulated therefrom and adapted to be connected by terminal wire H2 to the rectifier circuit of the fullwave bridging type H3 as shown by Fig. 11 of the drawings.

A windshield iii of tubular form is secured to the base of the funnel lilfi, as shown in Fig. 8 of the drawings to surround the electrodes it! and H18 and is provided with a perforated transverse partition H! which acts as a bafile for wind but permits the passage therethrough of water from the electrodes 10! and I08.

As most clearly shown in Figs. 7' and 10 of the drawings an annular supporting base member l is is secured to the underside of the funnel Hill by means of the downwardly extending brackets H9 and 28. lhe various electrical components of the snow detector such as the transformer Hi, the condenser 122, the high current relay M3 and the voltage sensitive relay lz l are all mounted on the annular base member H8.

With reference to Fig. 11 of the drawings, the circuit of the snow detector is shown to include the fullwave rectifier N3, the filter condenser 22, the current limiting resistor H5 and the sensitive relay EN. The carbon electrodes Hi1 and IE8 are connected in series with the transformer i2! and the fullwave rectifier I it so that when a circuit is established between electrodes i5! and its by the passage of water therethrough, the rectifier i it will be energized to supply direct current to the D. C. sensitive relay 24 which is thus operated to close the normally open relay contacts I26. When relay contacts I26 are closed the power relay i123 is energized to close normally open contacts I2! and connect the volt input terminals I23 and I31 to the output terminals l3! and 132 for energizing the heater coil on the wave reflector structure such as described in connection with Figs. 1 and 2 of the drawings. It is to be noted that thethermostatic relay switch m2 must be closed in response to outside temperatures of 35 or less before the transformer iii is connected to the line voltage and before the heater coil it! of the snow detector is connected to the line voltage. Thus the snow detector is not operative unless the outside temperature approaches the point at which snow and ice conditions may be expected.

It is seen from the above that there is provided a heating system for wave reflectors, such as is used. in the transmission. of microwaves, which is of relatively simple construction and which provides effective removal of ice and snow from the reflecting surface. The heating system may be automatically controlled so that energy is consumed only when heat is actually needed. As described above this may be done in various ways. lThe heating element may include one portion which is controlled in accordance with the temperature about the reflector, and a second portion which is controlled in accordance with a condition on the reflecting surface, such as the actual presence of ice or snow.

Although certain embodiments of the invention have been described, which are illustrative thereof, it is obvious that various changes and modifications can be made therein without departing from the intended scope of the invention as defined in the appended claims.

We claim:

1. A wave reflector device including in combination, a cup shaped member having a concave reflecting surface and a convex back surface, said cup shaped member including means for draining water therefrom, an elongated heating element positioned adjacent said convex back surface and being substantially uniformly positioned over the area thereof, and control means for energizing said heating element including a thermal controlled heating unit for heating a surface portion in accordance with the tempera ture about said device, and a control circuit including spaced electrodes positioned to receive therebetween water drained from said surface portion, to form a closed circuit for energizing said heating element.

2. A wave reflector device including in combination, a cup shaped member having a concave reflecting surface and a convex back surface, said cup shaped member including means for draining water therefrom, an elongated heating element positioned adjacent said convex back surface and being substantially uniformly positioned over the area thereof, and control means for energizing said heating element includingmeans positioned adjacent said reflecting surface for detecting the presence of ice or snow, said detecting means including a funnel-shaped surface and means for heating the same when the temperature falls below a predetermined value, said funnel-shaped surface having an opening at the apex thereof so that Water on said surface drains through said opening, and a control circuit including spaced electrodes positioned to receive therebetween water drained through said opening to form a closed circuit for energizing said heating element.

3. A wave reflector device including in combination, a cup shaped member having a concave reflecting surface and a convex back surface, said cup shaped member including means for draining water therefrom, an elongated heating element positioned adjacent said convex back surface and being substantially uniformly positioned over the area thereof, and control means for energizing said heating element including detecting means positioned adjacent said reflecting surface operative in the presence of ice or snow, said detecting means including a housing with a funnel-shaped top, a heating unit within said housing for heating said top to melt ice or snow thereon, said top having an opening at the apex thereof for draining water collected therein, a pair of spaced electrodes within said housing, a trough within said housing for applying water from said opening to said electrodes, a control circuit including said electrodes and a sensitive relay, a thermal controlled switch for connecting said heating unit and said control circuit to a source of voltage when the temperature adjacent said device falls below a predetermined value, and an energizing circuit including a power relay for connecting said heating element to a source of voltage, said energizing circuit being controlled by said sensitive relay to energize said heating element when water melted from said top of said detecting means is applied between said electrodes.

4. A wave reflector device including in combination, a cup shaped member having a concave reflecting surface and a convex back surface, an elongated heating element positioned adjacent said convex back surface and being substantially uniformly positioned over the area thereof, and control means for energizing said heating element including means positioned adjacent said reflecting surface for detecting the presence of ice or snow, said detecting means including a 'iunneL-shaped surface of cast material having high conductivity, a heating element embedded in said cast material for heating the same when the temperature falls below a predetermined value, said iunnel-shaped surface having an opening at the apex thereof so that water on said surface drains through said opening, and a control circuit including spaced electrodes positioned to receive therebetween water drained through said opening to form a closed circuit for energizing said heating element.

A wavereilector device including in combination, a cup shaped member having a concave reflecting surface and a convex back surface, an elongated heating element positioned adjacent said convex back surface and being substantially uniformly positioned over the area thereof, and control means for energizing said heating element including detecting means positioned adjacent said reflecting surface operative in the presence of ice or snow, said detecting means including a housing with a funnel-shaped top casting, a heating unit embedded in said top casting for heating the same to melt ice or snow thereon, said top casting having an opening at the apex thereof for draining water collected therein, a pair of spaced electrodes within said housing and positioned to receive water drained through said opening, a control circuit including said electrodes and a sensitive relay, a thermal controlled switch for connecting said heating unit and said control circuit to a source of voltage when the temperature adjacent said device falls below a predetermined value, and an energizing circuit including a power relay for connecting said heating element to source of volt age, said energizing circuit being controlled by sensitive relay to energize said heating element when water melted f om said top casting of said detecting means is applied between said electrodes.

6. A wave reflector device including in combination, a cup shaped member having a concave reflecting surface and a convex back surface, said cup shaped member including means for draining water therefrom, an elongated heating element positioned adjacent said convex back surface and being substantially uniformly positioned over the area thereof, and control means for energizing said heating element including detecting means positioned adjacent said reflecting surface operative in the presence of ice or snow, said detecting means including a housing with a funnel-shaped top casting, a heating unit embedded in said top casting for heating the same to melt ice or snow thereon, said top having an opening at the apex thereof for draining water collected therein, a pair of spaced electrodes within said housing and positioned to receive water drained through said opening, a windshield depending from the apex of said top casting and surrounding said electrodes, a control circuit including said electrodes and a sensitive relay, a thermal controlled switch for connecting said heating unit and said control circuit to a source of voltage when the temperature adjacent said device falls below a predetermined value, and an energizing circuit including a power relay for connecting said heating element to a source of voltage, said energizing circuit being controlled by said sensitive relay to energize said heating element when water melted from said top of said detecting means is applied between said electrodes.

'7. A wave reflector device including in combination, a cup shaped member having a concave reflecting surface and a convex back surface, an elongated heating element positioned adjacent said convex back surface and being substantially uniformly positioned over the area thereof, and control means for energizing said heating element including means positioned adjacent said reflecting surface for detecting the presence of ice or snow, said detecting means including a funnel-shaped surface and means for heating the same when the temperature falls below a predetermined value, said funnel-shaped surface having an opening at the apex thereof so that water on said surface drains through said opening, a. baflie in said opening to exclude the passage of solid materials therethrough, and a control circuit including spaced electrodes positioned to receive therebetween water drained through said opening to form a closed circuit for energizing said heating element.

8. A wave reflector device including in combination, a cup shaped member having a concave reflecting surface and a convex back surface, an

elongated heating element positioned adjacent said convex back surface and being substantially uniformly positioned over the area thereof, and control means for energizing said heating element including means positioned adjacent said reflecting surface for detecting the presence of ice or snow, said detecting means including a funnel-shaped surface and means for heating the same when the temperature falls below a predetermined value, said funnel-shaped surface having an opening at the apex thereof so that water on said surface drains through said opening, a control circuit including spaced electrodes positioned to receive therebetween water drained through said opening to form a closed circuit for energizing said heating element, and means adjacent said opening of said funnel-shaped surface and said electrodes for reducing the effect of wind on the water draining from said opening onto said electrodes.

9. A snow detector comprising a housing with a funnel shaped top casting, a heater unit embedded in said top casting for heating the same to melt ice or snow thereon, said top having an opening at the apex thereof for drawing water collected therein, a pair of spaced electrodes within said housing and positioned to receive water drained through said opening, a windshield depending from the apex of said top casting and surrounding said electrodes, a control circuit including said electrodes and a sensitive relay, a thermal controlled switch for connecting said heating unit and said control circuit to a source of voltage when the temperature surrounding said device falls below a predetermined value, and an energizing circuit including a power relay for controlling a system to be controlled, said energizing circuit being controlled by said sensitive relay when water melted from said top of said detecting means is received between said electrodes.

10. Apparatus for detecting the presence of ice and snow including in combination a housing having a funnel shaped top surface, means within said housing for heating said top surface when the temperature falls below a predetermined value, said funnel shaped surface having an opening at the apex thereof to permit water from said top surface to enter said housing, and a conii) trol circuit including spaced electrodes positioned to receive therebetween water from said opening to form a closed circuit therethrough, said control circuit including relay means and being arranged to operate said relay means when a closed circuit is provided between said electrodes, whereby said relay operates to indicate the presence of ice or snow on said top surface.

11. Apparatus for detecting the presence of ice and snow including in combination a housing having a funnel shaped top surface, means within said housing for heating said top surface when the temperature falls below a predetermined value, said funnel shaped top surface having an opening at the apex thereof to permit water from said top surface to enter said housing, a control circuit including spaced electrodes positioned to receive therebetween water from said opening to form a closed circuit therethrough, and means adjacent said opening of said funnel shaped top surface and said electrodes for reducing the effect of wind on the water passing through said opening onto said electrodes, said control circuit including relay means which is operated thereby when a closed circuit is provided between said electrodes, whereby said relay operates to indicate the presence of ice or snow on said top surface.

12. Apparatus for detecting the presence of ice and snow including in combination a housing having a funnel shaped top surface, means within said housing for heating said top surface when the temperature falls below a predetermined value, said funnel shaped top surface having an opening at the apex thereof to permit water from said top surface to enter said housing, a control circuit including spaced electrodes and relay means, and trough means within said housing adjacent said opening for applying water from said opening to said electrodes for providing a closed circuit therethrough, said control circuit providing a current for operating said relay means when a closed circuit is provided between said electrodes, whereby said relay operates to indicate the presence of ice or snow on said top surface.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,983,210 Wolcott Dec. 4, 1934 2,105,925 Mirriam Jan. 18, 1938 2,115,787 Runge May 3, 193-8 2,243,677 Lindenblad May 27, 1941 2,282,078 Morey May 5, 1942 2,527,864 Weidenschelling Oct. 10, 1950 FOREIGN PATENTS Number Country Date 645,235 Great Britain Oct. 10, 1950 

